1. Field of the Invention
The present invention relates to a multielement oscillator employing a higher mode planar resonator and used as a high-frequency oscillator in the millimeter band and microwave band, and more particularly to a multielement oscillator in which the performance is enhanced by increasing oscillating output.
2. Description of the Related Art
A high-frequency oscillator employing a planar resonator has been used as an oscillating source of frequencies in various units and apparatuses used in radio communication and an optical transmission system. One of this type of high-frequency oscillators is a multielement oscillator employing a higher mode planar resonator. This oscillator has a plurality of oscillating elements such as negative resistance devices and permitting the planar resonator to resonate at the higher mode to obtain an oscillating output. The multielement oscillator employing the higher mode planar resonator has drawn notice because it can be relatively easy in its design compared with an oscillator, in which a fundamental mode of the planar resonator is adapted, and can obtain a large oscillating output. This type of multielement oscillator has been referred to in, for example, ITE technical Report, Vol. 25, No. 6, pp. 15-18.
FIGS. 1A and 1B illustrate the constitution of a conventional multielement oscillator. The multielement oscillator is constituted by a higher mode planar resonator and a plurality of oscillating elements. The planar oscillator is a microstrip line resonator constituted by providing circuit conductor 2 for resonation on one of the principal planes of a substrate 1 consisting of, for example, dielectric material and by providing grounded conductor 3 on substantially the whole face of the other principal plane of substrate 1. Hereinafter, circuit conductor 2 for resonation will be referred to as resonating conductor 2.
Resonating conductor 2 has a substantially circular flat shape. Now, the higher mode made to be the TM21 mode having two pair of positive (+) and negative (xe2x88x92) potential points which are paired potential antinodes and arranged at positions in the outer circumference of resonating conductor 2 is applied to the planar resonator. In this case, the adjacent positive and negative potential points are disposed to be shifted 90 degrees to each other viewing from the center of resonating conductor, and identical electric potential points of respective of the positive and negative potential points are disposed at positions where they are mutually in a point symmetry. It should be noted that in the microstrip line type planar resonator, resonant electromagnetic field is generated by an electric field occurring between resonating conductor 2 and grounded conductor 3, and magnetic field according to this electric field.
As the oscillating elements, for example, Gunn diode 4 functioning as a negative resistance device is employed. On one of the principal planes of substrate 1, coupling lines 5 extend, respectively, from two mutually diametrical and identical potential points of resonating conductor 2, and each of coupling lines 5 is provided, at its extreme end, with a through-hole 8. Gunn diode 4 is embedded in each of these two through-holes 8. One and the other of the terminals of Gunn diode 4 are electrically connected to coupling line 5 and grounded conductor 3, respectively, by means of, for example, solder.
Further, on the one principal plane of substrate 1, output line 6 having a microstrip line structure is provided. Output line 6 is connected to resonating conductor at, for example, one of points which have reverse electric potentials to the identical potential points. To output line 6 is connected a capacitive matching line 7 for impedance matching.
In such a multielement oscillator, the oscillation frequency thereof mostly depends on resonance frequency of the planar resonator. Further, in such a multielement oscillator, it can be understood that two high-frequency oscillators sharing the planar resonator are formed so that respective high-frequency oscillators, i.e., Gunn diodes 4 are arranged so as to combine the outputs thereof. Thus, in comparison with the oscillator having only one Gunn diode, the multielement oscillator can nearly double the output thereof.
Nevertheless, the multielement oscillator employing the above-described higher mode constitution must encounter the following problems, caused by its arrangement in which Gunn diodes 4 are embedded in substrate 1 to be connected to coupling lines 5 and grounded conductor 3. That is to say, since the through-holes 8 provided in substrate 1 are formed by mechanical works, the accuracy in the positioning thereof is poor. Thus, the electric symmetry in the planar resonator must be deteriorated while making it difficult to obtain a desired oscillation frequency and further causing unfavored phase shift between the output frequencies from respective oscillating elements, i.e., Gunn diodes 4 to result in reduction in the oscillation output. Furthermore, this type of Gunn diodes 4 generates inductance components when they are mounted, and accordingly an additional reduction in the oscillation output occurs. Moreover, the works of through-holes 8 and embedding of the Gunn diodes in such through-holes for the mounting thereof become causes for lowering mass productivity of the oscillator.
An object of the present invention is to provide a multielement oscillator employing a higher mode planar resonator, and being superior in its easiness of design and capable of exhibiting a good efficiency in combining the power to thereby exert a large output.
The object of the present invention can be achieved by a multielement oscillator, which comprises: a planar resonator including a substrate, a first circuit conductor for resonation which is provided on a first principal plane of the substrate, and a second circuit conductor for grounding which is provided on a second principal plane of the substrate, the multielement oscillator being provided with a high-order resonance mode due to an electric field between paired plurality of positive and negative potential points and a magnetic field associated with the electric field; and a plurality of oscillating elements respectively connected, in at least one principal plane of the first and second principal planes, to a plurality of identical potential points of the planar resonator so as to be connected to paired circuit conductor portions formed in the one principal plane, wherein the multielement oscillator has an oscillation output corresponding to the high-order resonance mode.
In the present invention, since the oscillating elements are disposed in one of the principal planes of the substrate in which the resonating conductor is formed, so that the oscillating elements are connected between paired circuit conductor portions formed in the one principal plane, there is no need for providing through-holes in the substrate. Therefore, the manufacturing accuracy of the oscillator can be remarkably enhanced while making the working processes thereof easy, and the electric symmetry of the planar resonator can be maintained. Further, the inductance component of each oscillation element when it is mounted can be reduced. Accordingly, in accordance with the present invention, a multielement oscillator can be provided, which employs a higher mode planar resonator capable of improving efficiency in combining the power even in the band of ultrahigh frequency such as millimeter band, to thereby exert a large output.